Undergraduate students, Diana Wang and Tina Donaldson.

Part of the undergraduate experience in Physics at UNSW is doing real research in a real research lab. Tina Donaldson and Diana Wang did theirs in acoustics, where they were able to experience scientific research all the way from planning to publication — a rare experience for first year students.

The acoustics lab has developed a technique to study the acoustical response of the vocal tract. The technique measures the tract’s properties directly, rather than inferring them from the sounds produced. One of its first uses (by an honours student) was to study the resonances of the vocal tract used in the speech of a sample of young male university students—a sample drawn from the school’s teaching laboratories. Tina and Diana’s project was to study a comparable sample of young female university students and to compare the ‘vowel maps’, plots of the resonance frequencies that characterises vowel sounds in different languages and accents.

So they brought in their friends, made the measurements and, with a bit of help, did the analysis. The results appeared in a scientific paper, with their supervisors as coauthors. One of the figures from the paper shows that the resonance frequencies are higher for women, although the ratio is much less than the ratio of fundamental frequencies. Different length vocal tracts are one explanation, but social effects are probably important, too: whether you are tall or short you are likely to learn the accent appropriate to your sex.

Tina Donaldson, Diana Wang,
John Smith and Joe Wolfe

The frequencies of the first two resonances of the vocal tract for the eleven vowels of Australian English. The head and tail of each arrow are the mean values for women and men, respectively. The reversed axes are traditional in phonetics because such a plot closely resembles a plot of jaw height versus tongue position (front-back).